Diamond bit



J. M. KELLN ER DIAMOND BIT 2 Sheets-Sheet 1 Filed Aug. 27, 1962 4 0 9 I 9 6 5 m 5 6 7 K F T E. 4 1 I I 8 J Us. .1 5 .i 1 5 I L m fi/ 7 7 555 55 5 666777 6 8 0 w m 2 .l. 3 4 F I. -w .Zn 9 I c 3 1 PT 1H... 2 .I 3 r lmwmnwzlwz 232533333 JACKSON M. KELLNER INVENTOR.

BY E. Q-J- ATTORNEY Nov. 2, 1965 J. M. KELLNER 3,215,215

DIAMOND BIT Filed Aug. 27, 1962 2 Sheets-Sheet 2 JACKSON M. KELLNER INVENTOR.

BY Q

A T TORNEY United States Patent assignments, to Esso Production Research Company,

Houston, Tex., a corporation of Delaware Filed Aug. 27, 1962, Ser. No. 219,661 Claims. (Cl. 175-330) The present invention relates to rotary bits useful for drilling boreholes in the earth and is particularly concerned with an improved diamond bit which is more effective than bits available in the past.

The entrainment of cuttings and the removal of solids deposited by the drilling fluid as it infiltrates into the formation at the bottom of the borehole generally present serious problems during diamond bit drilling operations. The diamonds used on conventional bits are normally mounted in pads" which extend across the lower surface of the crown between radial or spiral watercourses. The watercourses are generally semicircular in cross-section, the rock formation forming the flat side at the base and the powdered metal matrix of the bit crown forming the upper semicircular portion. Drilling mud discharged into these watercourses flows under the lower surface of the bit parallel to the formation. A low velocity film or boundary layer of mud normally exists adjacent the formation, even though the linear velocities at which the fluid moves through the watercourses, about 200 to 250 feet per minute for example, are usually suflicient to produce turbulent flow. Due to the presence of this film or boundary layer, scouring of the formation by the mud stream and the entrainment of fine cuttings and solids deposited as mud fluids infiltrate into the formation occur only to a limited extent.

The effects of inadequate scouring of the formation at the bottom of the borehole during diamond drilling operations are serious. Diamond bits are ordinarily used in deep boreholes where extremely hard formations make the use of other bits unattractive. Hydrostatic pressures of 7500 p.s.i. or higher may be exerted by the drilling fluid against the formation at the bottom of the borehole. Because of the high pressure differential across the face of the formation, the mud fluids are rapidly forced into permeable strata beneath the bit; while the mud solids are retained on the formation surface. A cake of filtered solids quickly builds up and must be dislodged by the diamonds. This absorbs bit weight and rotary power, requires non-useful work, and is in part responsible for low drilling rates and premature bit wear. It also leads to clogging or balling effects due to the accumulation of fine cuttings and mud solids in the spaces between the exposed diamonds, the pads and the formation. It may result in over-heating of the bit, prevent adequate cooling and lubrication of the diamond bearing surfaces, and ultimately lead to matrix failure and premature loss of the diamonds. Efforts to overcome these and other difficulties caused by poor scouring of the formation and entrainment of cuttings and mud solids have been only partially successful. Such difliculties are encountered to some extent with most diamond bits.

It is therefore an object of the present invention to provide an improved diamond bit which will permit more efli'ective scouring of the formation beneath the bit than has generally been obtained with bits available in the past. A further object is to provide a bit beneath which drilling fluid can be discharged at high velocities in order to effectively entrain cuttings and mud solids and minimize their accumulation adjacent the diamond-bearing surfaces on the bit. Another object is to provide a bit which will permit fluid circulation at rates suflicient to reduce damage to the matrix and loss of the embedded diamonds on the bit. Still other objects will become apparent as the invention is described in detail hereafter.

In accordance with the invention, it has now been found that many of the difficulties encountered with diamond bits used in the past can be alleviated by utilizing bits provided with passageways which permit the discharge of drilling fluid at high velocities beneath the bit and the circulation of fluid upwardly adjacent the inner and outer surfaces of the crown. Studies have shown that the use of nozzles or similar discharge devices to obtain linear fluid velocities on the order of 200 feet per second or higher and thus provide effective scouring of the formation at the bottom of the borehole and the circulation of fluid at lower velocities adjacent both the inner and the outer crown surfaces to secure improved cooling and lubrication of the pads and diamonds result in more efficient entrainment of cuttings and mud solids, minimize difliculties due to clogging and balling of solids, reduce matrix failure and diamond losses, and generally permit higher drilling rates and longer bit life than can otherwise be obtained.

The nature and objects of the invention can best be understood by referring to the following detailed description of three embodiments of the improved bit and to the accompanying drawing, in which:

FIGURE 1 is a vertical elevation, partially in section, of a diamond core bit including multiple nozzles and passageways which permit the circulation of drilling fluid adjacent the inner and outer surfaces of the crown;

FIGURE 2 is a cross-sectional view of the bit of FIG- URE 1 taken about the line 22 in FIGURE 1;

FIGURE 3 is a bottom view of the bit shown in FIG- URES 1 and 2 in the drawing;

FIGURE 4 is a vertical elevation, partially in section, of an improved core bit intended for use in modified reverse circulation coring operations;

FIGURE 5 is a cross-sectional view of the bit of FIG- URE 4 taken about the line 5-5 in FIGURE 4;

FIGURE 6 is a bottom view of the bit depicted in FIG- URES 4 and 5;

FIGURE 7 is a vertical elevation of a drilling bit including passageways for the circulation of fluid upwardly adjacent both the inner and outer surfaces of the crown;

FIGURE 8 is a cross-section through the bit of FIG- URE 7 taken along the line 7-7; and,

FIGURE 9 is a bottom view of the bit depicted in FIGURE 7.

The diamond core bit depicted in FIGURE 1 of the drawing is shown connected to the lower end of a conventional core barrel including an outer section 11 and an inner section 12. The two sections are arranged concen trically to form an inner passageway 13 which holds the core and an outer, annular passageway 14 through which drilling fluid is circulated through the barrel. The bit itself includes body 15 and a crown 16 which is connected to the lower end of the body by means of threads 17. At its upper end, the body includes an annular recess 18 which extends parallel to the bit axis and contains internal threads 19 for connecting the bit to the lower end of the core barrel. In lieu of internal threads as shown, the upper end of the bit may be provided with a shank and external threads to form a standard A.P.I. tool joint 3 pin or may be fitted with other connecting means. An axial passageway extends through the body. The

upper end of this passageway is enlarged above an internal shoulder 21 against which the inner section of the core barrel seats. An O-ring or like member 22 of rubber, plastic or similar resilient material is set in a groove in the body above the shoulder to effect a seal between the body and inner section of the barrel. Lateral passageways 23 and 24, shown more clearly in FIGURE 2 of the drawing, extend through the wall of the body and slope upwardly toward the annulus surrounding the bit. Annular recess 25, similar to recess 18, is located in the body below the lateral passageways. As can be seen from FIGURE 2 of the drawing, longitudinal passageways 26 and 27 extend from one recess to the other between the lateral passageways. This permits the circulation of drilling fluid through the body. The bit shown thus includes a body consisting of a single member containing both longitudinal and lateral passageways. It will be apparent that the body could instead be constructed of concentric inner and outer members connected by conduits which serve as lateral passageways for the transmission of fluid between the center of the bit and the annulus surrounding the tool. Ease of fabrication may make this latter construction preferable in some instances.

The crown of the bit shown in FIGURE 1 includes an annular steel blank 30 surfaced with a metallic matrix 31 on the surface of which diamonds, chips of tungsten carbide or similar particulate cutting elements 32 are embedded. A typical matrix suitable for purposes of the invention may consist of a copper-nickel alloy containing powdered tungsten carbide in quantities suflicient to convey the required strength and erosion resistance. Other matrix compositions and methods for fabricating diamond bits are described in the Diamond Drill Handbook by J-. D. Cumming, 1956 edition, published by I. K. Smit and Son of Canada, Limited, Toronto. The blank is connected to the body by means of threads which mate with those on the lower end of the body. It is generally preferred to weld the blank and body together at the threaded joint as a final step in the fabrication process. The weld is indicated by reference numeral 33. A resilient ring 34 is set in grooves in the body and blank to provide a seal between the two and prevent the escape of fluid from the recess 25 into the axial passageway 20. The blank contains ports 35 which are aligned with the recess in the body. The bit shown contains eight ports spaced at regularintervals but a greater or lesser number spaced in a different manner may be utilized if desired. Nozzles 36 of tungsten carbide or similar erosion resistant material are embedded in the matrix section 31 of the crown below the blank 30. In the bit shown, the lower end of the blank is tapered to permit setting of the nozzles at a slight angle to the longitudinal axis of the bit. The nozzles discharge into recesses 37 in the lower surface of the crown.

The matrix section 31 of the crown extends laterally beyond the body to form the outer or gage surface 38 of the bit. Below the gage surface the matrix is rounded to form a generally convex annular surface 39 in which the diamonds or similar cutting elements 32 ar embedded. The matrix section extends upwardly a short distance into the axial passageway in the blank 30 to provide clearance between the inner wall of the bit and the core as it is cut. Nozzle recesses 37 containing the nozzles are located in the lower surface as pointed out above and are spaced at intervals about the tool. The nozzles are preferably located above the lower crown surface a distance such that the vena contracta is located above the face of the formation. The diameters of the recesses should be greater than the diameters of the areas over which the high velocity streams impinge against the formation. Radial grooves or watercourses 40 extending from the nozzle recesses across the inner and outer surfaces of the crown separate the crown. into pads and facilitate the flow of fluid from the nozzle recesses into the central passageway in the bit and into the annulus surrounding the tool. The arrangement of the nozzles, nozzle recesses and watercourses is shown more clearly in FIGURE 3 of the drawing.

The tool depicited in FIGURES 1 through 3 of the drawing is utilized by first connecting the bit to the core barrel and lowering it into place at the end of a conventional rotary drill string. Drilling mud or similar fluid is circulated through the drill string and withdrawn from the borehole annulus as the string is rotated. The mud passes downwardly through the annular space in the core barrel into upper recess 18 in the body of the bit. From here it flows through longitudinal passageways 26 and 27 into the lower recess and enters ports 35 in the crown section of the bit. Mud from the ports is discharged through nozzle 36 against the formation underlying nozzle recesses 37. The size of the nozzles is preferably such that the mud impinges against the formation with linear velocities on the order of 200 ft. per second or higher. The high velocity fluid impinging against the formation scours cuttings and mud solids from the face of the formation, preventing their accumulation and alleviating difficulties normally encountered due to balling and clogging of the bit. Drilling rates are improved because less regrinding of the cuttings is required and because the more effective removal of solids in part avoids high pressure differentials across chips in the formation.

The mud discharged at high velocities against the formation beneath the bit flows under the pads on which the diamonds are mounted and into the watercourses extending over the lower surface of the crown. The linear velocity is substantially reduced because the cross-sectional area of the flow path is substantially greater than the combined cross-sectional areas of the nozzles. Circulation beneath the pads is improved as a result of the scouring of the formation by the jet streams from the nozzles and better cooling and lubrication than might otherwise be obtained are secured. A part of the mud flows beneath the inner portion of the crown into the core opening at the center of the bit and passes upwardly to lateral passages 23 and 24, through which it is discharged into the annulus. The rest of the fluid flows beneath the outer portion of the crown into the annulus. The combined stream then passes upwardly through the annulus to the surface where it is discharged into the mud pit. This divided flow beneath the bit results in more effective cleaning than can generally be obtained where flow occurs in only one direction and thus permits higher drilling rates than can generally be secured with conventional core bits.

FIGURES 4, 5 and 6 of the drawing depict a further embodiment of the invention particularly intended for use in modified reverse circulation coring operations. This embodiments is shown in FIGURE 4 connected to the lower end of a drill string. The drill string is made up of concentric members 51 and 52 to form an axial passageway 53 through which the core cut by the bit is flushed to the surface and an annular passageway 54 through which fluid is supplied to the bit. Concentric drill strings which may be utilized in this manner are shown in U.S. Patent 2,657,016 and elsewhere in the art. The bit depicted includes a tubular body member 55 provided with an annular recess 56 at its upper end. Internal threads 57 permit attachement of the body member to the outer drill string section 51. The inner section of the drill string 52 fits into an axial passageway 58 in the body of the bit and seats against an internal shoulder 59 located therein. Ring 60 of rubber or similar material is set in a groove in the inner wall of the body and provides a seal between the bit and the inner section of the drill string.

Lateral passageways 61, 62 and 63 extend through the wall of the body member at spaced points about the bit periphery. The passageways slope downwardly from the inner wall of the body toward the annulus. The arrangement of the lateral passageways is shown more clearly in FIGURE 5 of the drawing. Interposed between passageways 61, 62 and 63 are longitudinal passageways 64, 65 and 66 which extend through the body member from recess 56 in the upper part of the members. The longitudinal passageways shown are of arcuate cross section and are equally spaced about the body. External threads 67 are provided at the lower end of the body member for connecting it to crown blank 68. The blank is an annular steel member containing a central opening 69 which is aligned with axial passageway 58 and openings 70, 71 and 72 which communicate with the longitudinal passageways in the body member. Crown matrix section 73 is bonded to the crown blank and contains nozzles 74, 75 and 76 of tungsten carbide or similar material. Orifices or other flow restrictions may be used in place of the nozzles. Each of the nozzles is inclined at a different angle to the longitudinal axis of the bit and discharges into a recess in the lower surface of the crown. As in the earlier embodiment, each nozzle preferably is located so that a vena contracta is formed before the discharged fluid impinges against the formation. Reference numeral 77 in FIGURE 4 indicates a cross section through one of the recesses. The use of a crown blank as described simplifies fabrication of the bit but is not essential. In some cases, the matrix section may be bonded directly to thelower part of the body member and the crown blank may thus be omitted.

As in the earlier embodiment, the crown of the bit extends laterally beyond the body member to form an outer or gage surface 78. The lower part of the crown is rounded to form a convex drilling surface 79 which extends across the bottom of the bit from the gage surface into the core opening at the center of the tool. The pads on the drilling surface are separated by junk slots 80. The junk slots extend from within the core opening to the upper edge of the gage surface and increase in width toward the gage. Nozzle recesses 77 are located in the pads and, as mentioned previously, are spaced at various distances fromthe center of the bit in order to secure more complete scouring of the formation at the bottom of the borehole. Watercourses 81, 82 and 83 extend from the nozzle recesses to the core opening and the borehole annulus above the outer portion of the crown. The sizes and configurations of the junk slots and watercourses are determined in part by the quantity of fluid to be discharged against the formation at the bottom of the borehole. The cross-sectional area of the junk slots and watercourses should be such that a substantial reduction in the linear velocity of the fluid will occur as the fluid flows outwardly from the nozzle recesses. Diamonds 84 or similar particulate cutting elements are embedded in the lower and gage surfaces of the crown.

The operation of the bit shown in FIGURES 4 through 6 of the drawing is generally similar to that of the earlier bit but differs in that the latter embodiment of the invention is intended particularly for use in modified reverse circulation coring operations. In such an operation, the bit is connected to the lower end of a con centric two-channel drill string and lowered into the borehole. Mud, air or other drilling fluid is introduced into the outer conduit of the drill string and circulated downwardly to the bit as the drill string is rotated. The drilling fluid enters recess 56 in the bit and passes downwardly through longitudinal passageways 64, 65 and 66. As it emerges from nozzles 74, 75 and 76 in the lower surface of the bit, the fluid impinges at high velocity against the formation at the bottom of the borehole. This results in the scouring of the formation and the entrainment of cuttings and mud solids from the formation face. The fluid stream is then divided, part of it passing inwardly to the core opening in the bit and the rest of it flowing outwardly to the annulus above the outer portion of the bit crown. The fluid in the annulus is at least in part diverted back into the bit through lateral passages 61, 62 and 63. A packer may be installed on the drill string above the bit to secure essentially complete return of the fluid or a heavy fluid may be maintained in the annulus to force return of the circulating fluid into the bit. The fluid and entrained cuttings flow to the surface through the central conduit in the drill string along with sections of the core cut by the bit.

The use of the bit of the invention for modified reverse circulation coring has pronounced advantages over the use of conventional diamond core bits in core drilling operations. The introduction of the drilling fluid into the borehole at points located beneath the crown of the bit avoids exposure of the annulus to full drilling fluid pressure. A substantial part of the initial pressure is dissipated as the fluid passes beneath the crown before it reaches the annulus. This avoids many of the formation fracturing and pressure parting difficulties normally encountered during reverse circulation coring operations in which the fluid is circulated from the annulus into the core opening near the center of the bit. The improved scouring of the formation obtained as a result of discharging the fluid at high velocities beneath the crown and better cleaning of the tool obtained due to the upward flow of fluid adjacent the inner and outer crown surfaces permits more efiicient entrainment of cuttings and mud solids and promotes more effective cooling and lubrication of the diamonds and diamond bearing surfaces. Difliculties due to balling and clogging of the bit are largely avoided. Drilling rates somewhat higher than those normally obtained with diamond core bits are secured.

FIGURE 7 of the drawing depicts still another embodiment of the invention which is intended for use in drilling operations where no core is recovered. The bit shown in FIGURE 7 includes an upper body member provided at its upper end with an opening 91 and internal threads 92 to form an A.P.I. tool joint box. Located below the threads in the body member is an annular recess 93. Longitudinal passageways 94, 95 and 96 extend downwardly from within this recess to a similar annular re cess 97 in the lower end of the body member in order to permit the passage of drilling fluid downwardly through the tool. The longitudinal passageways are shown in cross-section in FIGURE 8 of the drawing. An axial passageway 98 extends upwardly in the body member from its lower end and terminates at a point near the upper recess 93. Lateral passageway 99 and 100 extend from the axial passageway to ports in the outer surface of the body member. Three lateral passageways spaced at intervals between the longitudinal passageways are provided, although only two or these are shown in the drawing. Each lateral passageway slopes upwardly toward the outer surface of the body member. Threads 101 near the lower end of the body member are provided to permit assembly of the body member and the crown of the bit. An O-ring 102 is set in a groove in the lower surface of the body member to effect a seal between it and the crown.

The crown of the bit shown in FIGURES 7 through 9 includes a crown blank 103 of steel or similar material which is threaded to the lower end of the body member and a matrix section 104 which is bonded to the surface of the blank. The crown contains an axial passageway 105 aligned with passageway 98 in the body member and discharge passageways 106 which communciate with the lower recess 97 in the body member. Passageway 105 extends upwardly from an intake port in the lower surface of the crown near the bit axis. Only one of the discharge passageways is shown in FIGURE 7. Nozzles 107, 108 and 109, shown in FIGURES 7 and 9, are located in the lower ends of the discharge passageways and are held in place by snap rings 110, 111 and 112. O-rings 113, only one of which appears in the drawing, provide a seal between the nozzles and the inner walls of the discharge passageways. The nozzles are positioned so that fluid can be discharged at high velocities against the formation beneath recesses 114, 115 and 116 in the lower surface of the crown. These recesses are enlarged sections of watercourses 117, 118 and 119 which extend across the bottom of the crown, up the gage surface 120, and into axial passageway 105. Again, each nozzle is preferably positioned so that a vena contracta is formed in the discharged fluid before it impinges against the formation beneath the bit. Watercourses 121, 122 and 123 are located between those mentioned earlier and extend from the axial passageway into junk slots 124, 125 and 126 on the gage surface of the bit. A crows foot 127 is provided near the longitudinal axis of the crown to prevent the formation of a core in axial passageway 105 as the bit is rotated. Diamonds or similar cutting elements 128 are embedded in the matrix surface on the lower part of the bit.

The bit shown in FIGURES 7 through 9 of the drawing may be employed in conjunction with conventional rotary drilling apparatus. The bit may be lowered into place at the lower end of a drill string containing single channel pipe and drill collars. Drilling fluid is circulated downwardly through the string and into the upper end of the bit. The fluid supplied passes downwardly through the annular recesses, longitudinal passageways, and discharge passageways and emerges from the nozzles at high velocities. After scouring the formation beneath the recesses on the lower surface of the bit, the fluid flows through the watercourses and beneath the diamond bearing surfaces. The depths of the watercourses are preferably such that most of the fluid passes inwardly into the axial passageway in the tool and only a relatively small amount flows up the gage surfaces. This provides highly efiicient cooling, lubrication and entrainment of cuttings in the critical area near the center of the borehole where balling up, matrix damage and loss of diamonds are most apt to be encountered. The fluid and entrained cuttings entering the intake passageway adjacent the crows foot pass upwardly and are discharged through the lateral passage-' ways into the annulus. This fluid, together with that which flows upwardly about the gage surface of the crown, is then circulated through the annulus to the earths surface. Studies have shown that the circulation of drilling fluid upwardly through an axial passage in the crown and upwardly adjacent the gage surface of the bit as described normally results in substantially better performance than is generally obtained with conventional diamond bits.

What is claimed is:

1. A rotary drill bit comprising:

(a) a body member provided with means near the upper end thereof for connecting said bit to the lower end of a rotary drill string;

(b) a crown attached to the lower end of said body member for engaging the formation at the bottom of a borehole, said body member and crown containing a first fluid passageway extending from an opening in said body member above said crown to an opening in the lower surface of said crown near the longitudinal axis of said bit and a plurality of additional fluid passageways extending longitudinally in said body member and crown from openings near the upper end of said body member to discharge ports extending upwardly in the lower surface of said crown at points laterally displaced from the longitudinal axis of said bit;

(c) a plurality of annular flow restrictions located within said discharge ports to permit the discharge of fluid from said additional passageways against said formation at high velocity, said flow restrictions being recessed within said discharge ports a distance suflicient to permit formation of a vena contracta in the discharged fluid before said fluid impinges against said formation, said flow restrictions having throat diameters sufliciently small to give fluid discharge velocities in excess of about 200 feet per minute, and the lateral dimensions of said dischargeports adjacent the lower surface of said crown exceeding the diameters of the fluid impingement areas on said formation; and

(d) a plurality of particulate cutting elements embedded in the lower surface of said crown.

2. A rotary drill bit comprising:

(a) a body member provided with means near the upper end thereof for connecting said bit to the lower end of a rotary drill string;

(b) a crown attached to the lower end of said body member for engaging the formation at the bottom of the borehole, said body member and crown containing a first fluid passageway extending from an opening in said body member above said crown to a port in the lower surface of said crown near the longitudinal axis of said bit and a plurality of additional fluid passageways extending longitudinally in said member body and crown from inlets near the upper end of said body member to discharge ports extending upwardly in the lower surface of said crown at points intermediate said intake ports and the crown periphery;

(c) a plurality of nozzles mounted in said discharge ports for discharging fluid from said additional passageways against said formation at high velocity,

the outlet of each of said nozzles being recessed within a discharge port a sufiicient distance above the lower surface of said crown to permit formation of vena contracta in the fluid stream discharged from said nozzle before said stream impinges against said formation, the throat of each nozzle being sufliciently small to give a fluid discharge velocity in excess of about 200 feet per minute, and the lower end of each discharge port below the nozzle mounted therein being of greater diameter than the direct fluid impingement area on said formation beneath said nozzle; and

(d) a plurality of diamonds embedded in the lower surface of said crown adjacent said discharge ports.

3. A bit as defined by claim 2 wherein said port is a substantially circular opening at the longitudinal axis of said bit and said first pasageway is of circular cross section above said port.

4. A bit as defined by claim 2 including water courses extending across the lower surface of said crown from said discharge ports to the crown periphery.

5. A diamond drill bit comprising:

(a) a body member provided with means near the upper end thereof for connecting said member to the lower end of a rotary drill string;

(b) a crown connected to the lower end of said body member for engaging the formation at the bottom of a borehole, said body member and crown including an axial passageway extending upwardly therein from an opening in the lower surface of said crown near the longitudinal axis of said bit, a plurality of fluid passageways extending from inlets near the upper end of said body member to discharge ports extending upwardly in said crown at points laterally displaced from said axial passageway and a lateral passageway extending from an opening in said axial passageway to an opening in the outer surface of said body member above said crown;

(c) a plurality of erosion-resistant nozzles mounted in said discharge ports, said nozzles being recessed in said ports above the lower surface of said crown a sufficient distance to permit formation of a vena contracta in the discharged fluid before said fluid impinges against said formation, the throat diameters of said nozzles being sufficiently small to give fluid discharge velocities in excess of about 200 feet per minute, and said discharge ports being enlarged at the lower ends to prevent direct impingement of the discharged fluid on said crown; and

(d) a plurality of diamonds embedded in the lower surface of said crown about said axial passageway and said discharge ports.

References Cited by the Examiner UNITED STATES PATENTS Harding 175-330 X Williams 175-330 X Williams 175-330 X MacNeil 175-404 10 9/62 Edwards 175-330 1/ 63 Overly et al, 175-333 4/63 Henderson 2 175-60 X 12/63 Rowley 175-329 FOREIGN PATENTS 2/49 Australia. 10/ 60 France. 2/ 61 France.

Swart 175-340 10 CHARLES E. OCONNELL, Primary Examiner. 

1. A ROTARY DRILL BIT COMPRISING: (A) A BODY MEMBER PROVIDED WITH MEANS NEAR THE UPPER END THEREOF FOR CONNECTING SAID BIT TO THE LOWER END OF A ROTARY DRILL STRING; (B) A CROWN ATTACHED TO THE LOWER END OF SAID BODY MEMBER FOR ENGAGING THE FORMATION AT THE BOTTOM OF A BOREHOLE, SAID BODY MEMBER AND CROWN CONTAINING A FIRST FLUID PASSAGEWAY EXTENDING FROM AN OPENING IN SAID BODY MEMBER ABOVE SAID CROWN TO AN OPENING IN THE LOWER SURFACE OF SAID CROWN NEAR THE LONGITUDINAL AXIS OF SAID BIT AND A PLURALITY OF ADDITIONAL FLUID PASSAGEWAYS EXTENDING LONGITUDINALLY IN SAID BODY MEMBER AND CROWN FROM OPENINGS NEAR THE UPPER END OF SAID BODY MEMBER TO DISCHARGE PORTS EXTENDING UPWARDLY IN THE LOWER SURFACE OF SAID CROWN AT POINTS LATERALLY DISPLACED FROM THE LONGITUDINAL AXIS OF SAID BIT; 